Ski bases are usually produced using ultra-high molecular weight polyethylene (UHMWPE) derived from high density polyethylene (HDPE), either by extruding or sintering the material. Typically, any ethylene plastic with a molecular weight above 3.1 million is suitable for a ski or snowboard base. Other materials used for ski bases include polytetrafluoroethylene (PTFE, commonly known as Teflon™) and wood.
Ethylene-based skis, amongst others, have relatively low surface energies which reduces the tendency for water molecules to associate with the surface of the base, making them relatively hydrophobic. Hydrophobicity is defined in terms of the contact angle (θ) between a water droplet and a material surface. For a water droplet on a material surface, the contact angle is the angle between that material surface and a tangent of the droplet surface at the point where it meets the material surface. Superhydrophobic surfaces can be defined as having contact angles at or above 150°. Known artificial superhydrophobic materials are superhydrophobic by virtue of a thin surface coating designed for that purpose, but damage to or erosion of the coating causes a significant loss of the desired superhydrophobic properties.
Waxing the surface of a ski increases its hydrophobicity (increasing the contact angle of a water droplet from around 90° to around 110-120°), somewhat improving the ‘glide’ of the ski or snowboard over snow by reducing frictional forces between the hydrophobic base and the snow. This typically involves optimising the thickness of the thin film of water generated between the snow and the hydrophobic base, as well as balancing ‘wet’ and ‘dry’ friction. The greater the porosity of the base, the greater the improvement in ‘glide’ (up to a point) when wax is applied to the base as compared with the performance of a similar but non-waxed base. Some bases also have additives such as fluorocarbon powder or graphite, which further improve their ‘glide’.
Extruded bases are produced by melting the polyethylene, extruding it into a sheet and then cutting out the desired base shape. Such bases have properties that confer modest gliding interactions with snow if left unwaxed. This is due to its smooth, less porous surface, which is inexpensive to produce and requires minimal maintenance. By contrast, sintered bases are relatively expensive to produce, as the polyethylene must be ground into a powder, subjected to heat and pressure, and then sliced into shape, generating a different grain structure within the base relative to extruded bases. Sintered bases are more durable than extruded bases, and are also known to be faster on snow, when waxed. This is due to their inherently higher porosity which accepts wax more readily than extruded bases. However, they also require the application of wax to maximise their potential performance relative to extruded bases.
Waxes for skis are worn away during use (especially due to friction with ice) and are deposited onto the snow. This means the wax must be re-applied regularly. Such waxes often contain a wide variety of chemicals, the exact formulation of each being concealed as trade secrets by each manufacturer. However, certain compounds known to be in such waxes include fluorocarbons which can have a damaging effect on the environment. This applies especially where contaminated snow melts (particularly in spring, for non-permanent resorts) and carries the chemicals into the water table and other sources of water. It is also possible for the chemicals to become airborne if associated with water during normal evaporative processes. Given the known toxicity of chemicals in such waxes, local wildlife and plants can be adversely affected, damaging the local ecology. People who live in the area can also be similarly affected.
It is an object of the present invention to reduce or substantially obviate the aforementioned problems.